Method of making sprags



H. P. TROENDLY METHOD OF MAKING SPRAGS Aug. 28, 1956 Filed Feb. 2, 1950 atent h ice 2 ,760,259 Fatented Aug. 28, 1956 r/mrnon or r- SPRAGS Harry P. Troendly, Chicago, IlL, assignor to Borg-Warner Corporation, (Ihicago, BL, a corporation of Illinois This invention relates to one-way engaging devices and more particularly to such devices of the tilting sprag or gripper type.

A one-way engaging device of this type generally comprises opposite races between which the tiltable sprags are disposed. The races generally are cylindrical and one is inner with respect to the other. The tiltable grippers or sprags have curved surfaces which contact and engage the inner and outer races on tilting of the sprags so as to engage the device.

These races have generally been formed in two members in their exact cylindrical shape by grinding methods, that is, by stone grinding the races after they have been preliminarily hardened. Hardening operations generally cause some distortion in members of this type, and hence the necessity for grinding the races after hardening. The sprags, and particularly the curved race engaging surfaces of the sprags have generally been formed by grinding also, since for proper operation of the device, the surfaces must be quite accurately formed.

Stone grinding produces minute ridges and grooves in the material being ground, due to the fact that the grindin stones are made out of particles of material bonded together. These alternate ridges and grooves in both the races and in the engaging curved surfaces of the sprags result in ridge to ridge and point to point contact between the sprags and the races with the result that, in such one-way engaging devices, the rate of initial wear between the sprags and races is high and there is a subsequent poor engagement between the sprags and races due to the relatively large amount of material that is worn from the races and sprags. These ridge to ridge and point to point contacts between the sprags and races also result in high stresses in the sprags on the ridges produced by grinding on the curved sprag surfaces, so that there is a high frequency of breakage of the sprags.

It is an object of the present invention to provide engaging surfaces on the sprags which are much smoother and uniform than the ground surfaces of prior sprags and which do not contain the ridges and grooves resulting from grinding. More specifically it is an object to draw the sprags through dies for reducing their cross sectional shape and providing an arbasive action of the die on the race engaging surfaces of the sprags which I have found provides an extremely smooth surface and one free of ridges and grooves, whereby the rate of initial wear of the sprags on the races is materially reduced and the localized stress on the sprags is minimized.

It is another object of the invention to provide an im proved method for making the sprags in such a one-way device which includes, drawing a rod through dies for providing the smooth curved race engaging surfaces just described and then subsequently severing, preferably by shearing, sections of the formed rod from the body of the rod to form individual sprags.

It has been found that shearing sections of the formed rod produces end ridges or burrs on the otherwise smooth race engaging surfaces of the sprags, and, in order that these surfaces might be smooth and uniform from one end of the sprag to the other, it is an object to subsequently flatten and return to the original curved form the ends of the curved race engaging surfaces deformed in the shearing step. In this connection it is a more specific object of the invention to press the sprags after shearing between surfaces curved in the same manner as the race engaging surfaces to reform the ends of these sprag surfaces into their original shape and unify these surfaces.

The invention consists of the novel constructions, arrangements, devices and methods to be hereinafter described and claimed for carrying out the above-stated objects and such other objects as will appear from the following description of a preferred form of the invention and method for making the same, illustrated with reference to the accompanying drawing, wherein:

Fig. l is a fragmentary sectional view of a one-way engaging device embodying the principles of the invention;

Fig. 2 is a sectional view on a greatly enlarged scale taken on line 22 of Fig. 1;

Fig. 3 is a view showing a stone grinding operation on the outer race of the one-way engaging device illustrated in Fig. 1;

Fig. 4 is a sectional view through a die for a rod being formed thereby into the same cross sectional shape as the finished sprags;

Fig. 5 is a sectional view taken on line 55 of Fig. 4;

Fig. 6 is a cross sectional view of the rod used in connection with the die illustrated in Fig. 4 in the original form of the rod;

Fig. 7 is a view showing drilling and counter-sinking u operations on the rod shown in Fig. 4;

Fig. 8 is a view similar to Fig. 4 illustrating a rod being drawn through a forming die as a preliminary step to the drawing operation illustrated in Fig. 4;

Fig. 9 is a sectional view taken on line 9-9 of Fig. 8;

Fig. 10 is a view showing sprag severing and reforming operations used on the sprag rod after it has been formed as shown in Figs. 4 and 8; and

Fig. 11 is a sectional view taken on line 11-11 of Fig. 10.

Like characters of reference designate like parts in the several views.

Referring now to the drawing and in particular to Fig. 1, the one-way clutch device illustrated in this figure may be seen to comprise a pair of members 10 and 11 either of which may constitute a driving or driven member. The member 10 is formed with a cylindrical outer surface 12 constituting a race, and the member 11 is formed with an inner cylindrical surface 13 also constituting a race. The races face each other as shown, and a series of tiltable sprags or grippers 14 are disposed between the races.

Each of the sprags 14 has an outer arcuate race engaging surface 15, an inner arcuate race engaging surface 16 which is eccentric with respect to the surface 15' as is apparent from an inspection of the drawings and flat surfaces 17 and 18 between the arcuate surfaces. An opening 19 is provided through each of the sprags, and a garter spring 26 extends through these openings. The sprags fit between the races 12 and 13 in such a manner that the spring 29 is stressed into a wavy form as shown in Fig. l, and the spring tending to return to its original round form tends to tilt the sprags into radial positions with their fiat sides 17 and T18 extending radially with respect to the cylindrical races 12 and 13. A cage or retainer 21 of any suitable construction may be provided between the races 12 and 13 for holding the sprags positioned between the races.

In operation, assuming tha the member 11 is rotated in a direction as indicated by the arrow A with respect to the member 10, the sprags 14 tend to rotate still farther out of radial position with respect to the cylindrical races 12 and 13 than the positions in which the sprags are shown, and the sprags disengage with respect to the races and slip on the races. Assuming, on the other hand, that the member is rotated opposite to the direction indieated by the arrow A with respect to the member 10, the spring 20 in tending to come into its original round form and the relative motion between the members It) and 11 tend to tilt the sprags 14 into radial positions with respect to the cylindrical races 12 and 13, and the sprags engage between the races. The one-way engaging device is then engaged so that motion is transmitted opposite the direction indicated by the arrow A from the member 11 to the member 10. It will be understood, of course, that the member 10 could be the driving member instead of the member 11 in which case, rotation of the member 10 in the direction indicated by the arrow A will cause engagement of the sprags between the inner and outer races and will lock the oneway engaging device.

The one-way engaging device thus far described may be manufactured by means of the method now to be described. Each of the races 12 and 13 of the members 10 and 11 respectively is ground as by means of a cylindrical rotating stone 22 (see Fig. 3). The members 10 and 11 are first preliminarily formed with the races 12 and 13 by any suitable method, as by means of a turning lathe, for example, and the members 10 and 11 are then heat treated to harden them. This heat treating on members of this shape generally causes some distortion so that the races 12 and 13 are not absolutely cylindrical at this time. The stone 22 is then utilized for grinding the races 12 and 13 into substantially perfect cylindrical form. It will be understood that the stone 22 is driven at a relatively high speed while the member 11 rotates relatively slowly with the stone in contact with the race 13 and grinding it into correct form. The showing in Fig. 3 is of the stone 22 in contact with the race 13; however, it will be understood that the race 12 on the member 10 may be ground in substantially the same manner.

The stone grinding operations just described leave minute grinding ridges 23 and grooves 24 therebetween as are shown in Fig. 2, which is drawn on a greatly enlarged scale with respect to Fig. 1. These ridges and grooves are present, as will be understood, on both the races 12 and 13. If the surfaces 15 and hid the sprags 14 were also ground so that there would be similar grinding ridges and grooves on these surfaces, it is apparent that there would be point to point or line to line contact between surfaces 15 and 16 and the races 12 and 13, and it has been found with such constructions that there is high initial wear between the sprags and races during which the ridges on the sprags and races are ground down due to wear. This point to point and line to line contact of the sprags on the races also causes high and excessive local stresses in the sprags, so that the sprags tend to break under such stresses. 1 remedy these troubles by providing the sprags 14 with arcuate surfaces 15 and 16 which are much smoother than could be obtained by stone grinding, so that the contact between the sprags 14 and races 12 and 13 is much closer to a surface to surface contact than is obtained if all of the surfaces 12, 13, 15 and 16 are stone ground.

The sprags 14 are formed from a length of round rod 25 (see Fig. 6). The rod is drawn through a number of dies, the final one of which is indicated by the reference numeral 26 in Fig. 4, which change its cross sectional shape from round to the cross sectional shape of the finished sprags as shown in Fig. 5. The final shape of the rod shown in Fig. includes the flat surfaces 17 and 18 and the arcuate surfaces 15 and 16 which are the same shape as the corresponding surfaces on the finished sprags. One of the preliminary forms of die is shown in Figs. 8 and 9, being indicated by the reference numeral 26a and has flat surfaces 17a and 18a and arcuate surfaces 15a and 16a corresponding to the surfaces 17, 18, 15 and 16 respectively. It will be noted that the shape of the die 26a is intermediate the final shape shown in Fig. 5 and the original round shape of the bar shown in Fig. 6. The bar is drawn through the dies by any suitable means, such as the tongs 27 shown in Fig. 4, being drawn preliminarily through the die 26a and finally through the die 26, to cause the rod 25 to have the exact cross sectional shape of the finished sprags 14.

It will be understood that a number of other dies similar to the dies 26 and 26a are utilized along with the latter dies. Some of these other dies have openings intermediate in shape between the form of the die shown in Figs. 8 and'9 and the round form of the rod 25 and still others have openings therein intermediate the final cross sectional shape of the sprag shown in Fig. 5 and the intermediate cross sectional shape shown in Fig. 9. The rod 25 is drawn successively through these dies to change its cross sectional shape successively into forms more and more approximating the cross sectional shape shown in Fig. 5 until finally the final die 26 is reached and the rod 25 is drawn therethrough in order to provide the rod with the final cross sectional shape.

The drawing operations through the dies provide very smooth arcuate surfaces 15 and 16 on the finished rod. Grinding marks or similar marks are absent from the surfaces. The dies 26 and 26a and the other intermediate dies are preferably metal, being made from tungsten carbide, for example, and the dies give very exactly formed cross-sections of rod passed therethrough. The rod is drawn through the dies in cold condition, although an annealing operation may be given to the rod for relieving stresses after some intermediate die has been utilized.

After the rod 25 has been formed with the exact crosssection of the finished sprags by being drawn through the die 26, the holes 19 are drilled through the rod by means of a drill 28, and the holes 19 are countersunk by means of a countersink 29. The individual sprags are then sheared from the rod, as for example by use of the shear 30 shown in Fig. 10 which comprises a stationary tube 31 through which therod 25 is moved in the direction of the arrowB and a tube 32 which is movable with respect to the tube 31 and shears across its end. Both of the tubes 31 and 32 have substantially the same cross sectional shape as the finished sprag, as shown in Fig. 5. For forming an individual sprag 14, the rod 25 is fed through the tube 31 and after a length of rod 25 equal to the length of a finished sprag has passed through the tube 31 and into the tube 32 while the latter tube is aligned with the tube 31, then the tube 32 is moved downwardly in the direction of the arrow C to shear off a section of the tube 25 and form the sprag. The rod 25 is intermittently given this movement into the tubes 31 and 32 when they are 7 aligned and between such intermittent movements ofthe rod 25, the tube 32 is sheared across the end of the tube 31 for severing the individual sprags from each other. The sprags are accumulated in the tube 32 as'shown.

I have found that the shearing of the rod 25 into the individual sprags has the effect of forming small burrs orridges'on the ends of the race engaging surfaces 15 and 16 at the planes of shear. Such end ridges or burrs, if allowed to remain on these surfaces 15 and 16 would, of course, function muchlike ridges 23 on the surfaces 15 and 16, if the surfaces. 15 and 16 were ground like the surfaces 12 and 13 of the members 10 and 11, to cause high initial wear and point to point contact of the sprags on the races, and I remove these burrs by means of a pressing operation. The individual sprags 14 as they are intermittently moved through the tube 32, by intermittent movement of-the rod 25 into the tube 31, move out. of the tube 32 and onto a table or platen 33. Ashas been described, this movement of the sprags 14 through the tube 32 is while the tubes 32 and 31 are aligned, and the platen 33 is on the sam: level as the lower surface 31a of the tube 31.

A pair of pressure members 34 and 35 are disposed on opposite sides of the platen 33 and are provided respectively with end surfaces 36 and 37 of the same arcuate shapes as the race engaging surfaces 15 and 16 of the sprags. During movement of the tube 32 across the tube 31 to shear a sprag 14 from the rod 25, the pressure member 35 is moved toward the pressure member 34 which is held stationary, so as to compress the sprag which has just previously been moved onto the platen 33 between the surfaces 36 and 37. This compression of the sprags 14 between the members 34 and 35 has the effect of flattening out any burrs or end ridges on the race engaging surfaces 15 and 16 formed on the sprags 14 by the shearing operation, so that the surfaces 15 and 16 of the sprags are uniformly smooth from one end of the sprag to the other. It is, incidentally, contemplated that the movable member 35 may have only a very small movement such as .020", for example. The member 35 is moved back again after this pressing operation just prior to the return of the tube 32 into alignment with the tube 31, so that the rod 25 and the sprags 14 in the tube 32 and on the platen 33 may again be moved to put another length of rod 25 into the tube prior to shearing ofl this length of rod to form a sprag 14.

The sprags 14 as they come from the shearing and pressing steps shown in Figs. and 11 may be heat treated by any standard method to harden and temper them. Due to the compact shape of the sprags, the heat treatment does not cause any substantial distortion of them, and the race engaging surfaces 15 and 16 remain smooth and arcuate. The sprags may then be tumbled in a tumbling barrel (not shown), for example, to remove any additional burrs, as for example on their ends, and to clean them, and the sprags may then be checked for hardness on a standard machine for this purpose and may then be measured to make certain that they are within certain tolerances. The sprags within these tolerances may then be classed according to measurement into three groups, for example, with the sprags of each group being of the same size within closer tolerances. The sprags are then assembled between members 10 and 11 to form finished one-way engaging devices with the sprags in any one engaging device all being from one of these groups. It will be understood that after the shearing and pressing operation shown in Figs. 10 and 11, the sprags can be immediately assembled between members 10 and 11 for forming finished one-way engaging devices; however, I have found that for producing engaging de vices which will wear longest, it is well to put the sprags through the operations just mentioned, including the heat treatment.

I wish it to be understood that my invention is not to be limited to the specific constructions, arrangements, devices and methods shown and described, except only insofar as the claim may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

In a method of making non-round sprags for a one-way engaging device having opposite eccentrically curved surfaces adapted to engage opposite coaxial races on tilting of the sprags, the steps which comprise passing a rod through a die of the same cross sectional shape as the sprags to form the rod with this cross sectional shape with said curved sprag surfaces being finished smooth by the die, intermittently moving the formed rod through a shear having a stationary part with a channel through which the rod may move and a movable part having a channel which receives the sprags and shears across the end of the stationary part, severing sprags from the rod by moving said movable part across the stationary part between such intermittent movements of the rod, passing the sprags from the movable shear individually onto a stationary platen by such movements of the rod, and compressing the sprags on platen between two pressure members having pressure faces of the same shape as the curved sprag surfaces at times when the movable part is moving to shear a sprag, for returning any end burrs on the sprags formed by shearing back into the curved sprag surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,542,040 De Lavaud June 16, 1925 1,701,736 Timken Feb. 12, 1929 1,834,722 Mullen Dec. 1, 1931 1,839,909 Weatherhead Jan. 5, 1932 1,851,031 Baldwin Mar. 29, 1932 2,346,462 Southwell Apr. 11, 1944 2,540,457 Rice Feb. 6, 1951 FOREIGN PATENTS 669,464 Germany Dec. 28, 1938 

